A girl who is strung along by a boy during the Wintertime purely for sexual gratification, to be inevitably dumped in the Summertime when the going is easy.
If the girl falls in love too soon, is high-maintenance, or pleads to spend more time with her boyfriend than he is willing to offer, the relationship may end abruptly, shortly before Xmas or Valentines Day. But if the girl finds conditions to be congenial and bites her tongue the relationship will run early- to mid-Summer, at which point she is discarded so her ex-boyfriend can go on the holiday he secretly booked solely for himself when they were still together.
Dylan: You're the perfect winter warmer
Kristine: What did you just call me?
Dylan: Oops! I mean, we'll always be together
Dylan: Yeah sure :p